The invention relates to a rack and pinion steering system, and in particular, to a rack bushing which slidably supports a rack shaft within a steering body.
A conventional rack and pinion steering system is illustrated in FIG. 5 where a substantially cylindrical rack bushing 102 is disposed around the inner surface of a bushing holder 100 which is secured to a steering body, not shown, for slidably supporting a rack shaft 104. The inner peripheral surface of the bushing holder 100 is formed with an annular groove 100a while one end of the rack bushing 102 is formed with an outwardly extending flange 102a, which fits in the annular groove 100a in the bushing holder 100 to lock it against withdrawal. A clearance 106 is defined between the outer peripheral surface of the flange 102a of the rack bushing 102 and the bottom surface of the annular groove 100a in the bushing holder 100.
In the rack and pinion steering system constructed in the manner mentioned above, a load in the form of an impact which is directed oblique or perpendicular to the axis of the rack shaft 104 may be transmitted through a tie rod when steering upon a bad road. Such load acts upon the inner surface of the rack bushing 102 in the region of the end 102b around its inner periphery where the flange 102a is formed, tending to urge such end 102b outward. As a consequence, the outer peripheral surface of the rack bushing 102 is subject to a surface pressure of an increased magnitude from an upper edge 100c of a chamfer 100b formed on the sidewall of the annular groove 100a formed in the bushing holder 100, causing the likelihood that the durability of the rack bushing 102 may be endangered by being cracked.